Reciprocating electric motor



' Nov. 29, 1927. 1,651,306

c. s; WEYANDT RECIPROGATING ELECTRIC IOTOR Filed men s. 1924 IllDial/4273M I Patented Nov. 29, 1927,

UNITED STATES PATENT OFFICE.-

CARL S. WEYANDT, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO CENTRAL ELEC-TRIO TOOL COMPANY, A CORPORATION OF PENNSYLVANIA.

RECIPROCATING ELECTRIC MOTOR.

Application filed March 5,1924. Serial No. 697,053.

This invention relates to electric motors of the reciprocating type andparticularly to motors suitable for use percussive tools.

The object of my invention to provide a reciprocating motor suitable foruse as an electric hammer, embodying novel features of construction byreason of which a high degree of efiieiency is attained, and thestructure assembled into a compact unit.

In practicing my invention I dispose an actuating winding around abarrel or cylinder of non-magnetic material or metal within which a coremember of magnetizable material is reciprocated by the influence of thewinding. In order to reduce the reluctance of the magnetic circuit ofthe motor, I compose the magnetic circuit of a plurality of sets oflaminations of magnetizable material of high permeability such assilicon teel. The laminations are substantially rectangular in shape andextend radially from the barrel almost encircling the Winding. The sideof the rectangleadjacent the barrel is provided with an air gap. The twoportions separated by the gap terminate in tipswhich are perpendicularto the length of the gap and extend through openings in the barrel towithin a few thousandths of an inch from the inner surface of the barrelwhich is engaged by the moving core. By reason of the magnetic circuitof low reluctance, the

leakage flux is reduced to a minimum. Since the tips of the laminationsare disposed very close to the core, substantially the entire magneticflux is concentrated upon the core to actuate it in either direction.With this construction the efliciency of the motor is considerablyincreased over that heretofore attained.

Figure 1 of the accompanying drawings is a diagrammatic view of anelectric hammer system containing an electric hamn'rer constructed inaccordance with my invention;

Figure 2 is a longitudinal view partially in section and partially inelevation, of the hammer illustrated in Figure 1 Figure 3 isj-asectional view, taken later"- ally. of the liammer'sliown, in Figure 2.

Figures 4 and 5 are elevational side and barrel or guide for the core orstriking element; and

Figure 7 is a transverse septional view of the barrel illustrated inFigure 6.

As illustrated in the diagram in Figure 1, energy is derived from analternating current circuit and transn'iitted through an electric valve21, to an electric hammer 22 of the reciprocating motor type.

The electric valve 21 here illustrated is of the electronic type,comprisingan electron-emitting element, such as a filament 23,

as .a cathode, and a plate 24: as an anode.

A transformer 25 supplies energy to the filament cathode 23 to render itincandescent and electron-emitting to establish an operative conditionin the valve 21 for transmitting current waves of one polarity to thehammer 22.

The hammer 22 comprises, as may be seen in Figures 2 to 7, inc, anoperating coil or solenoid 26, a movable core 27 controlled thereby, abarrel or guide 28 of non-magnetic material, such as bronze, for thecore 27, coaxially disposed in the coil 26, laminated magnetic circuitconductors 29 for directing the magnetic force developed by the coil 26,a casing 31 enclosing the coil and the laminated magnetic circuitconductors 29, and a handle 32 provided with a trigger switch 33 forcontrolling the operation of the hammer.

The laminated magnetic circuit conductors 29 comprise two members of Lshape 34 hav- 1 .ing a base portion 35 and a side or radially extendingportion 36, and a straight connecting member 37. Some of the L-shape members 34 are provided with tips 38 disposed at the ends of the baseportions 35, that are adapted to lit tightly in openings 39 in thebarrel. 1

The laminations 29 are arranged in sets or groups as illustrated inFigures 3, 4 and 5. The inner laminations of each set comprise thoseprovided with the tips 38 that fit tightly in the barrel. Thelaminations thus serve the twofold purpose of locking the coil 26 inpredetermined position relative to the barrel 28, and of directing andconcentrating the magnetic flux at the most-effective position toinfluence the core.

.The tips 38 extend through the side of the barrel to within a fewthousandths of an inch from the inner surfaceof the barrel 28, which isengaged by the core in its recipro- 26,- as illustrated in Fig. 3.

eating movements. The relatively short air gap between the tips of eachset of laminations reduces the reluctance of the magnetic circuit to aminimum value and insures a highly eflicient magnetic circuit having arelatively small amount of magnetic leakage.

The sets of laminations are disposed radially around the barrel 28 andthe coil The separate air gaps of the respective sets togetherconstitute an air ga of annular shape which is adaptcd to be bridged orshunted by the core 27 in its reciprocating movements.

The barrel 28 serves as a guide for the core 27 and as a supportingstructure for the different elements whereby they may be assembled intoa compact unit. The barrel comprises a cylindrical tube of bronzeprovided with the openings 39 to receive the tips 38 of the laminations.The barrel 28 is preferably provided with slots 39 extendinlongitudinally thereof and entirely through the wall of the barrel tointerrupt its circumferential continuity between the pole tips 38 spacedlongitudinally of each other axially of the barrel or in the directionof movement of the core 27, to reduce the wasteful currents induced inthe barrel 28 by fluctuations ,in the magnetic field at and between thetips 38. Preferably, these slots 39 extend between apertures 39 in whichare received the pole tips 38. The forward end of the barrel is threadedto receive an'open end cap 41 provided with a threaded opening Withinwhich a tool guide 42 is disposed. The tool guide 42 is 1'0- videdwithan opening within and through which the shank of a tool 43, such as adrill, chisel, rivet set or the like, may be disposed in the path oftravel of the core 27. The rear or handle end of the barrel is providedwith an enlarged flange-like cylinder 44 that is externally threaded.The end of the barrel at the cylinder 44 constitutes a seat 45, for aspring-cushioned back stop 46. A spring 47 is disposed between the backstop 46 and a cap 48 which together with the cylinder 44 fits into arecess in the end member 44 threaded on the barrel extension 44, andcarrying the handle 32. The member 44 co-operates With the end surfaceof the cylinder 44 to secure the cap 48 in position. The outer surfaceof the base of the cylinder 44 joins the outer surface of the barrel toconstitute a shoulder 49 against which and member 44 the rearlaminations 34 are seated.

Although the barrel should be of non-magnetic material, any non-magneticmaterial will not be satisfactory merely because of its non-magneticcharacter. A barrel employed in such an application, as a guide for areciprocating element of steel, such as the core must be, requires, inaddition to a nonmagnetic characteristic, physical characteristics ofhardness, toughness and high tensile strength. The barrel must be hardto resist abrasive action of the core, and must be tough and have a hightensile strength to resist stresses set up by the end plate 41 and themember 44 in tightly securing all the parts as a unit.

I have found that a bronze barrel having a content of about 60% copper,39% zinc and from traces to 1% manganese, has the qualities andcharacteristics essential for a barrel employed as a guide in areciprocating motor or electric hammer. Such a barrel resists abrasiveaction of a reciprocating core and permits tightly securing all parts toform a compact unit, as is illustrated in Fig. 2.

The respective dimensions of the tool shank and the core should be suchthat when oneend of the core engages the end of the tool shank, asillustrated in Fig. 2, the other end should. be within the path ofmagnetic influence of the laminations. One end of the core should alwaysbe subject to the influence of the magnetic flux at the extremepositions of the core. The backstop 46 should accordingly have suchdimensions as to insure that the core will extend into the flux fieldwhen the stop is engaged.

In assembling the 'hammer theL-shape laminations on the right hand orleft hand side are first placed in position, in and around the barrel.Two fibre washers 51 are placed around the barrel on the inside of thelaminations. The opposite sets of L- shape laminations are then placedin position. A layer of insulation 52 is wound over the surfaces of thebase portions of the L-shape laminations and the portion of the barrelbetween the tips. The insulation 52 serves to hold the L-shapelaminations in position while the operating coil 26 is wound on thebarrel, and also serves to hold the fibre washers 51 in position againstthe sides of the perpendicular or lateral portions 36. After the coil iswound upon the barrel, the straightlaminated portions 37 are placed inposition and secured to the L-shape portions by suitable means such asrivets 53. The backstop parts are then placed in position and the member44 is securely threaded onto the barrel. The casing 31 is placed aroundthe coil, the core 27 is inserted through the front end of the barreland the front end cap 41 is threaded on to the barrel to clamp thecasing and groups of laminations 29 securely between the end cap and themember 44. The magnetic field structure comprising the groups oflaminations 29, with the coil 26 between the end portions of each group,is accordingly held or clamped between the end members 41 and 44threaded upon the barrel 28: and similarly, the housing or casing 31 isheld between the members 41 and 44*. The

mined distance from the front surface of the backstop. Vhen a toolhaving a shank of predetermined length isinserted through the toolguide, the core will be held in the magnetic path when engaging the toolshank, and proper operation of the core will be ensured.

\Vhen operation of the hammer is desired, the trigger switch 33 isclosed and connects a relay switch 55 to the circuit 20. The relayswitch 55, when closed, connects one terminal of the operating coil ofthe hammer to the circuit conductor (30 through the electronic valve 21.The other terminal of the coil being already connected to circuitconductor 61, the valve transmits alternate current waves, that is, onlycurrent waves of the same polarity, to the operating coil.

The operation of the valve 21 is such that when the filament is negativewith respect to the plate, current is transmitted by the valve, but whenthe filament is positive with respect to the plate or anode, no currenttraverses the valve. The valve may therefore be regarded as transmittingpositive waves or impulses.

Assuming the core 27 to be in the position illustrated in Figs. 1 and 2when the trigger switch is closed, the first positive alternation orcurrent wave will traverse the valve .21 and energize the operating coil26 to estab lish a magnetic flux field across the annular air gapbetween the laminations 34. The core will be pulled backward toward thebackstop 46. When the core reaches the central part of the barrel thepositive alternation or current wave diminishes to zero 'alue and thewinding then remains unenergized until the next positive alternationbegins. During the interval between the positive waves, however, thecore continues its travel on its own momentum or inertia, from thecentral region of the barrel until it engages the backstop 46. Y At thattime the second positive alternation traverses the valve and theoperating coil, and the magnetic flux is reestablished across the airgap. The core is then pulled forward to strike the end of the tool shanktodeliver a workingblow to the tool.

The coil becomes de-energi'zed about the time the core reaches themiddle region of the barrel and again ,the core continues its travelduring the interval until the coil is again energized. Suchreciprocating action of the core continues in synchronism with thetransmitted current waves so long as the trigger switch is held closed.When the trigger switch is opened the magnet switch opens and the valveis disconnected from the operating winding. The hammer thereupon ceasesoperatlng.

The principal effective air gap of the reciprocating motor abovedescribed is that existing between the inner ends of the laminae 35,andmore particularly between their tips 38, at the left, Fig. 2, and theinner ends of the laminae 35, and more particularly, their tips 38, atthe right, spaced longitudinally of the axis of the barrel 28 andwinding 26, from the laminae and tips at the left. The magnetizable core27 in its movement across the air gap shortens the gap andeventuallybridges it. The air gap 18 a minimum length when the core 27 is inbridging position. In any event, the core 27 in any stroke passes theposition of minimum air gap length, continuing on until it impacts uponthe tool or until, in the return stroke, it impacts upon the butl'erblock -16.

A feature of my construction is the magnetic circuit of thefield-producing means comprising'magnetizable field core membersdisposed adjacent the path of movement of the core and pointing towardseach other, but falling short of each other, to form an air gapintermediate the ends of thefield structure or between the ends of themagnetizing winding such as 26. A further feature resides in suchcombination provided with magnetizable material disposed outside of thewinding and substantially magnetically coupling the aforesaid coremembers, whereby -the reluctance of the magnetic circuit is low.

By means of a magnetic circuit of the character described herein, thereluctance and leakage losses are reduced to a minimum and the entireactive flux is concentrated upon the core at the most advanta geousposition. Moreover, all parts are assembled and securely locked into acom pact unit.

My invention comprehends', therefore. a reciprocating motor of novelconstruction, whereby a relatively high efliciency is obtained, and theprocess of assembling the cle ments into a compact unit is simplified.It is contemplated, of'course, that changes may be made in the structureor the design of the different elements without varying theircooperative relation or departing from the spirit and scope of thisinvention as set forth in the appended claims.

Certain of the subject matter herein disclosed, particularly theelectric circuit arrangements and the employment of an electric valve orthe like for controlling energization of the motor, is not hereinclaimed. but is claimed in my application Serial No. 697,054, filedMarch 5, 1924.

This application is a continuation in part of. application Serial No.527,037. filed January 4, 19 22, and relating to methods of operatingelectric tools; 7

I claim as my invention 1. An electric hammer of the reciprocating motortype comprising a winding, a core axially movable therein, a barrel orguide for the core axially disposed relative to the core, and meanscomprising magnetic conductors for locking the coil in predeterminedposition relative to the barrel or guide and for concentrating thedeveloped magnetic flux at a predetermined region of the barrel orguide. i

2. A reciprocating electric motor comprising an actuating coil, a coreresponsive there to, a longitudinally slotted member within which saidcore travels, and means constituting a magnetic circuit for the coilarranged to present an annular air gap to be bridged by the core in itsmovement.

3. A reciprocating electric motor comprising an actuating coil, a coreresponsive thereto, a slotted, hollow member to guide said core, andlaminations of substantially C- shape encircling the coil and radiallydisposed relative to said guide member to present an annular air gapadjacent the path of travel' of the core. 7

4. A reciprocating electric motor comprising' an actuating coil, a coreresponsive thereto, and groups of lamina spaced from each othercircumferentially of said core,

, comprising laminations having radially exing magnetic circuitconductors having their opposed faces tapered to concentrate themagnetic flux of the coil at a predetermined region of the barrel.

6. An electric hammer unit comprising an actuating coil, a movable coreor striker element responsive thereto, a barrel or guide surrounding thecore, magnetic lannnations between which the coil is disposed andlocking it in position relative to the barrel, an end cap fixed at thefront end of the barrel and provided with a guide to align an in-'sorted tool in the path of the movable core. a cylinder casing enclosingthe coil and laminations, and a rear cap con'iprising a handle fixed atthe rear end of the barrel and cooperating with the other end cap ton'iaintain the casing in position.

7. A reciprocating electric motor comprising an actuating Winding, acore responsive thereto, and a magnetic circuit for the windingcomprising spaced magnetizable members having tapered, opposed faceswhich form an air gap that is substantially closed by the core duringits movement in each dircction.

S. A reciprocating electric motor comprising an actuating winding, acore responsive thereto, and a magnetic circuit for the windingcomprising pole extensions Within said winding having ends taperedtoward tips to concentrate the magnetic flux of the winding at a regionadjacent the path of travel of said core.

9. An electric hammer of the reciprocating motor type suitable for doinguseful work through the medium of a tool or element to be recurringlystruck, comprising an actuating winding, a movable core or str kerelement responsive thereto for striking the tool or element on itsforward stroke, a backstop for the core on its backward stroke, anabutment limiting movement of said backstop in one direction, a springnormally maintaining said back-stop in engagement with said abutment,and means for concentrating the magnetic field of the winding at aregion between the end of the tool and the backstop.

10. A reciprocating electric motor comprising a winding, a core movablethereby between two predetermined points and means constituting amagnetic circuit for the winding and presenting an air gap adjacent thepath traversed by the core, a yielding backstop for the core on itsbackward stroke, and an abutment to limit the forward movement of saidback-stop, the relative dimensions of the core, its path of travel andthe air gap being such that one end of the core will lie in the fluxfield between the air gap limits when at either of its extreme positionsin its path of travel.

11. In a reciprocating electric motor, the combination with a winding, acore responsive thereto and. a barrel serving as a guide for the coreand a support for the winding, of means for precluding relativelongitudinal movement between the winding and the barrel comprising melr'ns disposed at each end of the winding ovided with locking tips ortenons fitting into the barrel.

12. In an electric hammer of the reciprtr eating motor type, thecombination with an actuating winding, a core )OflSlVG thereto, and abarrel or guide for the core serving also as a support for the winding.of means for concentrating the magnetic flux developed by the windingcomprising magnetic circuit members secured to the barrel by tenonsextending into the barrel.

13. In an electric hammer of the reciprocating motor type, thecombination with an actuating winding, a core responsive thereto, and abarrel or guide for the core serving as a support for the winding, ofmeans for concentrating the magnetic flux developed by the windingcon'iprising magnetic circuit members embodying tcnons of magneticmaterial extending into the barrel to secure the magnetic membersthereto.

14. In a reciprocating motor the combination comprising a solenoid, asolid core lUU lui;

llu

lllu

therefor susceptible to its influence, and means for conducting themagnetic flux of the solenoid to a region closely adjacent the path oftravel of the core, the flux conducting means being of such character asto present. less reluctance to the flux than the core would through apredetermined portion of the flux path.

15. In a reciprocating motor, the combination comprising a solenoid, ahollow. conducting member having slots therein to reduce'eddy currentlosses, a solid core reciprocatlng therein, and laminated magneticcircuit conductors for conducting the solenoid flux to a region withinwhich the flux need traverse only a relatively small portion of thesolid core, thereby obviatingexcessive eddy current losses in the core.

7 16. A reciprocating motor comprising a solenoid, a movable coreresponsive thereto, and meansfcomprising magnetizable members havingtapered ends terminating in tips for directing the magnetic flux to aregion including a portion of the core when disposed at either extremityof its travel.

17 An electric hammer comprising a solenoid, a movable core responsivethereto, a

hollow member in'which said core reciprocates, a tool having its shankdisposed in the path of travel of the core to be struck thereby, a toolguiding member secured to one end .of said hollow member, a backstop forthe core, means for concentrating the magnetlc flux of the solenoidbetween the tool shank or the backstop and the corresponding impactsurface of the core, and a handle for said hammer secured to the otherend'of said hollow member. I

18. An electric hammer comprising a solenoid, a movable core responsivethereto, a hollow member in which said core reciprocates, a tool havingits shank disposed in the path of travel of the core to be struckthereby, 'a yielding backstop for the core .movable within an extensionof said hollow member, and magnetic circuit members radially disposedabout the solenoid for concentrating the solenoid flux to establish an.annular magnetic field between the tool shank or the back-stop and thecorresponding impact surface of the core.

19. A reciprocating motor comprising a solenoid, a movable cor'eresponsive thereto, a barrel between the solenoid and the core servingas a guide for the core and provided atone end thereof with an annularshoul der, and laminated magnetic circuit conductors disposed in groupscircumferentially of the barrel and securely seated against t e shoulderand locked in such position by tips fitting into the barrel.

20. A reciprocating motor comprising a netic circuit conductor elementsfor the solenoid comprisi-n elements almost surrounding a section 0% thesolenoid and extending through the tubular member to approximate ly theinner surface of said member.

21. A reciprocatin field-producing win ing, a magnetizable corereciprocated thereby, field core members extending outwardly from thepath of travel of said ,core .and spaced from each other longitudinallyof the path of movement of said core, at least one of said field coremembers extending longitudinally of motor comprising a 1 the path ofsaid core toward the other field travel of said core and spaced fromeach other longitudinally of the path'of move ment of said core, atleast one of said field core members extending longitudinally of thepath of said core toward the other field core member to effect an air gawith respect to which said core is movab e past the position of minimumair gap length, a hollow member in which said core reciprocates, andyielding back-stop disposed in an extension of said hollowmember, ahandle for the motor secured to said extension, and a spring positionedbetween said yielding backstop and said handle.

23. A reciprocating motor comprising a reciprocating magnetizable core,a guide member therefor of non-magnetic metal of a character resistingabrasion by said core and having longitudinally extending slotstherethrough, laminated field ole structure on said guide member disposeadjacent the path of movement of said core upon said guide member, and amagnetizing winding surrounding said core and guide member formagnetizing said field pole structure.

24. A reciprocating motor comprising a hollow member having openingstherein, a magnetizable core reciprocating within. said member, fieldcore structure having pole tip structure extending into said openings,and a core-actuating winding for magnetizing said laminations.

25. A reciprocating motor comprising a v hollowmember, a magnetizablecore reciprocating within said member, circumferentially spaced groupsof field lamlnations maintained in spaced relation to each otherlongitudi'nally of the movement of said core member by openings in saidmember which receive extensions on said laminations, and

extending toward each other to form air gaps with respect to which saidcore-is movable, and means for magnetizing said groups of laminations.

26. A reciprocating motor comprisinga hollow member, a magnetizable corereciprocating within said member, field core structure having pole tipstructure extending through said member adjacent the path of movement ofsaid core, and means for magnetizing the field core structure.

27. A reciprocating motor comprising a hollow conducting member, amagnetizable core reciprocating therein, and field pole members spacedfrom each other longitudinally of the path of movement ofthe core toform an air gap with respect to which the core is movable, said memberbeing slotted within the region of the air gap to interrupt itscircumferential continuity.

28. A reciprocating motor comprising a .hollow conducting member, amagnetizable core reciprocating therein, said member having aperturesspacel longitudinally with respect to the path of movement of said core,and field pole members terminating at said apertures to form an air gapwith respect to which said core is movable, said member having a slotbetween said apertures to interrupt its circumferential continuity.

29. A reciprocating motor comprising a hollow member, a magnetizablecore reciprocating within said member, circumferentially spaced groupsof field laminae having portions extending outwardly from said memberand portions extending along said member, field laminations spacedlongitudinally of said member from said last named portions to form acircumferential series of air gaps with respect to which said core ismovable, members secured to the ends of said hollow member in abuttingrelation to said laminations, and means for magnetizing said groups oflaminations.

30. A reciprocating motor comprising a hollow member, a corereciprocating therein, end members secured to said member adjacentopposite ends thereof, field pole mem- .bers disposed between said endmembers and spaced from each other longitudinally of said hollow memberto form an air gap between the ends of said hollow member, and a windingsurrounding said hollqw member and disposed between said field polemembers.

31. A reciprocating motor comprising a hollow member, a corereciprocating therein, end members secured to said member adjacentopposite ends thereof, lield pole members disposed between said endmembers and spaced from each other longitudinally of said hollow memberto form an air gap between the ends of said hollow member, a windingsurrounding said hollow member and disposed between said tield polemembers, and a casing enclosing said-winding and said field pole membersand extending from one of said end members to the other.

A reciprocating motor comprising a reciprocating magnetizable core, andmeans for actuating said core comprising field poles spaced from eachother longitudinally of'the movement of the core to form an air gap,said poles having faces inclined toward said gap, and a magnetizingwinding having a length greater than said air gap, said core having alength to bridge said air gap and moved by the field produced by saidwinding to a position beyond said bridging position.

33. A reciprocating motor comprising a reciprocating magnetizable core,and means for actuating said core comprising field poles spaced fromeach other longitudinally of the movement of the core, inwardly directedtipson said poles to form an air gap, said poles having faces inclinedtoward said tips, and a magnetizing winding longer than said air gap andextending to both sides thereof for moving said core with respect tosaid air gap past the position of minimum air gap length.

In testimony whereof, I have hereunto subscribed my name this 29th dayof Febru- CARL s. WEYANDT.

